Response of arboreal Collembola communities to the conversion of lowland rainforest into rubber and oil palm plantations.

BACKGROUND: In the last decades, Southeast Asia has experienced massive conversion of rainforest into rubber and oil palm monoculture plantations. The effects of this land-use change on canopy arthropods are still largely unknown. Arboreal Collembola are among the most abundant canopy arthropods in tropical forests, potentially forming a major component of the canopy food web by contributing to the decomposition of arboreal litter and being an important prey for canopy arthropod predators. We investigated abundance, richness, and community composition of, as well as the influence of a series of environmental factors on, canopy Collembola communities in four land-use systems in Jambi Province, Sumatra, Indonesia: (1) lowland rainforest, (2) jungle rubber (rubber agroforest), and monoculture plantations of (3) rubber and (4) oil palm. RESULTS: Using canopy fogging in 32 research plots in both the dry and rainy seasons in 2013, we collected 77,104 specimens belonging to 68 (morpho) species. Generally, Collembola communities were dominated by few species including two species of the genus Salina (Paronellidae; 34% of total individuals) and two species of Lepidocyrtinae (Entomobryidae; 20%). The abundance of Collembola in lowland rainforest (53.4 ± 30.7 ind. m-2) was more than five times higher than in rubber plantations, and more than ten times higher than in oil palm plantations; abundances in jungle rubber were intermediate. Collembola species richness was highest in rainforest (18.06 ± 3.60 species) and jungle rubber (16.88 ± 2.33 species), more than twice that in rubber or oil palm. Collembola community composition was similar in rainforest and jungle rubber, but different from monoculture plantations which had similar Collembola community composition to each other. The environmental factors governing community composition differed between the land-use systems and varied between seasons. CONCLUSIONS: Overall, this is the first in-depth report on the structure of arboreal Collembola communities in lowland rainforest and agricultural replacement systems in Southeast Asia. The results highlight the potentially major consequences of land-use change for the functioning of arboreal arthropod food webs.

Rainforest conversion to rubber and oil palm reduces abundance, biomass and diversity of canopy spiders.

Rainforest canopies, home to one of the most complex and diverse terrestrial arthropod communities, are threatened by conversion of rainforest into agricultural production systems. However, little is known about how predatory arthropod communities respond to such conversion. To address this, we compared canopy spider (Araneae) communities from lowland rainforest with those from three agricultural systems in Jambi Province, Sumatra, Indonesia, i.e., jungle rubber (rubber agroforest) and monoculture plantations of rubber and oil palm. Using canopy fogging, we collected 10,676 spider specimens belonging to 36 families and 445 morphospecies. The four most abundant families (Salticidae N = 2,043, Oonopidae N = 1,878, Theridiidae N = 1,533 and Clubionidae N = 1,188) together comprised 62.2% of total individuals, while the four most speciose families, Salticidae (S = 87), Theridiidae (S = 83), Araneidae (S = 48) and Thomisidae (S = 39), contained 57.8% of all morphospecies identified. In lowland rainforest, average abundance, biomass and species richness of canopy spiders was at least twice as high as in rubber or oil palm plantations, with jungle rubber showing similar abundances as rainforest, and intermediate biomass and richness. Community composition of spiders was similar in rainforest and jungle rubber, but differed from rubber and oil palm, which also differed from each other. Canonical Correspondence Analysis showed that canopy openness, aboveground tree biomass and tree density together explained 18.2% of the variation in spider communities at family level. On a morphospecies level, vascular plant species richness and tree density significantly affected the community composition but explained only 6.8% of the variance. While abundance, biomass and diversity of spiders declined strongly with the conversion of rainforest into monoculture plantations of rubber and oil palm, we also found that a large proportion of the rainforest spider community can thrive in extensive agroforestry systems such as jungle rubber. Despite being very different from rainforest, the canopy spider communities in rubber and oil palm plantations may still play a vital role in the biological control of canopy herbivore species, thus contributing important ecosystem services. The components of tree and palm canopy structure identified as major determinants of canopy spider communities may aid in decision-making processes toward establishing cash-crop plantation management systems which foster herbivore control by spiders.

Historical and future climate change fosters expansion of Australian harvester termites, Drepanotermes.

Past evolutionary adaptations to Australia's aridification can help us to understand the potential responses of species in the face of global climate change. Here, we focus on the Australian-endemic genus Drepanotermes, also known as Australian harvester termites, which are mainly found in semiarid and arid regions of Australia. We used species delineation, phylogenetic inference, and ancestral state reconstruction to investigate the evolution of mound-building in Drepanotermes and in relation to reconstructed past climatic conditions. Our findings suggest that mound-building evolved several times independently in Drepanotermes, apparently facilitating expansions into tropical and mesic regions of Australia. The phylogenetic signal of bioclimatic variables, especially limiting environmental factors (e.g., precipitation of the warmest quarter), suggests that the climate exerts a strong selective pressure. Finally, we used environmental niche modeling to predict the present and future habitat suitability for eight Drepanotermes species. Abiotic factors such as annual temperature contributed disproportionately to calibrations, while the inclusion of biotic factors such as predators and vegetation cover improved ecological niche models in some species. A comparison between present and future habitat suitability under two different emission scenarios revealed continued suitability of current ranges as well as substantial habitat gains for most studied species. Human-mediated climate change occurs more quickly than these termites can disperse into newly suitable habitat; however, their role in stabilizing arid ecosystems may allow them to mitigate effects on some other organisms at a local level.

Changes in diversity and community assembly of jumping spiders (Araneae: Salticidae) after rainforest conversion to rubber and oil palm plantations.

Rainforest conversion into monoculture plantations results in species loss and community shifts across animal taxa. The effect of such conversion on the role of ecophysiological properties influencing communities, and conversion effects on phylogenetic diversity and community assembly mechanisms, however, are rarely studied in the same context. Here, we compare salticid spider (Araneae: Salticidae) communities between canopies of lowland rainforest, rubber agroforest ("jungle rubber") and monoculture plantations of rubber or oil palm, sampled in a replicated plot design in Jambi Province, Sumatra, Indonesia. Overall, we collected 912 salticid spider individuals and sorted them to 70 morphospecies from 21 genera. Salticid richness was highest in jungle rubber, followed by rainforest, oil palm and rubber, but abundance of salticids did not differ between land-use systems. Community composition was similar in jungle rubber and rainforest but different from oil palm and rubber, which in turn were different from each other. The four investigated land-use systems differed in aboveground plant biomass, canopy openness and land use intensity, which explained 12% of the observed variation in canopy salticid communities. Phylogenetic diversity based on ~850 bp 28S rDNA fragments showed similar patterns as richness, that is, highest in jungle rubber, intermediate in rainforest, and lowest in the two monoculture plantations. Additionally, we found evidence for phylogenetic clustering of salticids in oil palm, suggesting that habitat filtering is an important factor shaping salticid spider communities in monoculture plantations. Overall, our study offers a comprehensive insight into the mechanisms shaping communities of arthropod top predators in canopies of tropical forest ecosystems and plantations, combining community ecology, environmental variables and phylogenetics across a land-use gradient in tropical Asia.

Spiders in rice-paddy ecosystems shift from aquatic to terrestrial prey and use carbon pools of different origin.

Spiders are important bio-control agents of rice insect pests such as plant- and leafhoppers. To investigate temporal changes in spider prey and variations in prey due to landscape structure around rice fields, carbon and nitrogen stable isotopes of rice field arthropods were analysed over three consecutive sampling dates during the rice cropping season. Initial isotope composition of gnats and midges emerging from submersed rice fields indicates a larval algae diet, while later values suggest a switch to rice-derived carbon. Initial δ13C values of plant- and leafhoppers were higher in fields of rice-heterogeneous landscapes, indicating migration from source populations feeding on C4 grasses into rice fields; later, their δ13C values approached those of rice. Isotope values of web-building and cursorial spiders in the earliest samples indicate aquatic gnat and midge prey. The later shift toward terrestrial herbivore prey was more pronounced for small than for larger species and in rice paddies near permanent vegetation, indicating use of prey from the surrounding landscape. The results suggest that rice field spiders are supported by three different carbon pools: (1) aquatic carbon originating from algae and (2) legacy carbon from previous growing cycles, both incorporated via between-season predation on gnats and midges, and (3) carbon from the current rice season incorporated via herbivore prey. In conclusion, fostering aquatic midge and gnat larvae, e.g. via mulching, and integrating rice fields into rice-heterogeneous landscapes likely strengthens biological control of pest species in rice paddies by supporting high populations of spiders between cropping seasons.

Costs of pleometrosis in a polygamous termite.

Costs and benefits of pleometrosis, as understood from social Hymenoptera, have never been tested in the independently evolved termites. To understand the extent to which such co-founding may be advantageous for colony survival and growth, we tracked the survival and reproduction of 5000 laboratory-established incipient colonies of the facultatively polygamous neotropical termite Nasutitermes corniger. Significantly more pleometrotic groups than monogamous queen-king pairs failed within the first 90 days of establishment, and 99 per cent of pleometrotic groups lost at least one founding member. Oviposition commenced earlier in larger groups, but colony growth was slower and production of workers and soldiers was delayed compared with pairs. Thus, pleometrosis does not increase colony fitness and is in fact highly disadvantageous.

Heterospecific pairing and hybridization between Nasutitermes corniger and N. ephratae.

The sympatric neotropical termites Nasutitermes corniger and Nasutitermes ephratae are clearly distinguishable based on morphology, nest architecture, defensive secretion composition, and molecular markers. However, given the extensive ecological, geographical, and behavioral overlap of these closely related species, the potential for interbreeding may exist. To explore this possibility, heterospecific pairs were formed experimentally to examine courtship and colony-establishment behaviors, and reproductive potential. Courtship and nest construction behavior occurred in heterospecific pairs in a similar manner to that of conspecific pairs. Survival of pairs depended upon the species of the female partner. N. ephratae females paired with N. corniger males produced as many offspring as conspecific pairs. N. corniger females mated to N. ephratae males, however, produced significantly fewer offspring at 60 days post-establishment than the reciprocal cross or conspecific N. ephratae or N. corniger pairs. This was also the only pairing in which any aggression was observed. Heterospecific pairs and groups formed in mate choice mesocosms, suggesting that species recognition between these two termites is not an important aspect of mate choice. Overall, species mismatch tolerance and hybrid offspring viability are high. The present data, together with previous evidence from defensive secretions and isozyme analysis, suggest that hybridization may periodically occur in nature, and that reproductive barriers between these two species may be incomplete. Hybridization could provide a rare but important source of genetic diversity and may ensure mating opportunities for the more abundant sex of alates in each species.

Global biodiversity and phylogenetic evaluation of remipedia (crustacea).

Remipedia is one of the most recently discovered classes of crustaceans, first described in 1981 from anchialine caves in the Bahamas Archipelago. The class is divided into the order Enantiopoda, represented by two fossil species, and Nectiopoda, which contains all known extant remipedes. Since their discovery, the number of nectiopodan species has increased to 24, half of which were described during the last decade. Nectiopoda exhibit a disjunct global distribution pattern, with the highest abundance and diversity in the Caribbean region, and isolated species in the Canary Islands and in Western Australia. Our review of Remipedia provides an overview of their ecological characteristics, including a detailed list of all anchialine marine caves, from which species have been recorded. We discuss alternative hypotheses of the phylogenetic position of Remipedia within Arthropoda, and present first results of an ongoing molecular-phylogenetic analysis that do not support the monophyly of several nectiopodan taxa. We believe that a taxonomic revision of Remipedia is absolutely essential, and that a comprehensive revision should include a reappraisal of the fossil record.

Mate preference and disease risk in Zootermopsis angusticollis (Isoptera: Termopsidae).

Termites face significant and chronic intranidal selection pressures from parasites and pathogens that colonize their nests. They also encounter microbes outside their nest while foraging and during dispersal of winged primary reproductives to establish new colonies. The latter run the additional risk of becoming infected by a mating partner. Indeed, death of reproductives because of disease is a major cause of incipient colony failure and may favor prescreening prospective mates for signs of illness. To determine the role of disease on mate preference in termites, female primary reproductives of the Pacific dampwood termite Zootermopsis angusticollis (Hagen) simultaneously were presented with reproductive males that were either healthy or exhibiting a progression of symptoms associated with infection by the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff Sorokin). We compared duration and frequency of female visits to healthy and infected males. In addition, we determined the physiological consequences for females exposed to fungal conidia, either directly or indirectly through their mate. Females showed no preference for healthy rather than infected males. Moreover, only directly-exposed females experienced negative physiological effects, having a reduced chance of survival, gaining less weight, developing fewer functional ovarioles, and producing significantly fewer vitellogenic oocytes than controls. Although there are important fitness-related costs of direct exposure, the lack of mate selection based on disease risk suggests that more imminent ecological pressures (e.g., predators, desiccation) override the need for a careful and time-consuming assessment of a potential mate's health.